1. Field of the Invention
Embodiments of the present invention generally relate to playing streaming digital media such as digital video or digital audio. More specifically, embodiments of the present invention relate to bit rate stream switching on networked client devices.
2. Description of the Related Art
Digital content distribution systems typically include a content server, a content player, and a communications network connecting the content server to the content player. The content server is configured to store digital content files available for download from the content server to the content player. The digital content files correspond to, e.g., movies, televisions shows, sporting events, music productions, etc. The digital content file typically provides sequential content data, organized according to playback chronology, including audio data and/or video data.
The content player (e.g., a Blu-Ray® disc player) is configured to download and play a digital content file, in response to a user request. The process of playing the digital content file includes decoding and rendering audio and video data to generate audio and video signals sent to audio speakers and a display screen. Playback typically involves a technique known as “streaming,” where the content server transmits digital content to the content player, which plays the digital content file while content data is being received. To account for variable latency and bandwidth within the communications network, a content buffer queues the incoming content data ahead of the content data actually being played. During moments of network congestion, which leads to lower available bandwidth, less content data is added to the content buffer, which may drain down as content data is being de-queued to support playback at a certain playback bit rate. However, during moments of high network bandwidth, the content buffer is replenished and additional buffer time is added until the content buffer is generally full again. In practical systems, the content buffer may queue content data corresponding to a time span ranging from seconds to more than a minute.
Streaming digitally encoded audiovisual (AV) programs over the Internet including feature length films and television programs has become increasingly popular as the availability of high-bandwidth Internet communication has increased. AV programs are digitally encoded using a compression algorithm executed by a coder-decoder unit or codec. The visual and auditory quality of a program, when played by the content player, depends significantly on the bit rate at which the program is encoded by a codec. In digital audio and video applications, bit rate refers to the number of data bits used per unit of playback time to represent audio and video. In general, the higher the bit rate the higher the visual and auditory quality of a program and the longer it takes to download a portion of the program over a data network at a fixed bandwidth or transmission rate. In practice, each digital content file stored on the content server may be encoded using a variety of different bit rates. That is, the content server may encode the same media title using a variety of bit rates (and encoding schemes). Prior to initiating playback, the content player may measure available bandwidth from the content server and select a digital content file having a bit rate that can be supported by the measured available bandwidth. To maximize playback quality, the content player may select to stream the digital content file with the highest bit rate that does not exceed the measured bandwidth.